In the process of injection molding, hot molten thermoplastics are periodically injected into a cold mold. Without mold temperature control, the cavity surface will be heated unevenly due to the constant supply of heat from the molten plastic. Therefore, temperature control is a major prerequisite for achieving high molding quality.
A typical temperature control system 99 for a mold is represented in FIG. 5. The temperature control system 99 is shown in use in a mold apparatus. The mold apparatus includes a housing 92 and a media cavity 93 defined therein. The temperature control system 99 includes a control panel 94, a heat exchanger 95, a heater 96, a first electromagnetic valve 98 and a second electromagnetic valve 97. The control panel 94 is located on the housing 92. The mold body 102 also defines therein a media channel (not shown) communicating with the media cavity 93. The media cavity 93 is filled with a media fluid, which flows in the channels for heating or cooling the housing 92 during molding. The heat exchanger 95 is disposed in the media cavity 93, and the heater 96 is disposed on the outside of the media cavity 93 for heating the media fluid. The heat exchanger 95 is connected with the controlling panel 94 and the second electromagnetic valve 97 for controlling the mold cooling process. The heater 96 is connected with the controlling panel 94 and the first electromagnetic valve 98 for controlling the mold heating process. In use, the heater 96 heats the media cavity 93. Then, the media cavity 93 further heats the media fluid. The media fluid transmits the energy to the mold cavity. When cooling, the heat exchanger 95 is filled with cooling water which carries energy from the media fluid so as to decrease the temperature of the mold. Users may control the first electromagnetic valve 98 and the second electromagnetic valve 97 by means of the controlling panel 94 thus enabling the user to control the heating and cooling processes of the mold. However, conventional temperature control systems use an electrical method of heating. This method consumes large amounts of electrical energy both in the heating and in the cooling processes of the mold.
Therefore, a new temperature control system is desired in order to overcome the above-described problems.